How to sizing capacitor for power factor correction?

To properly sizing the amount of capacitor (kVAR) required to correct the lagging power factor,we must have three (3) important of information below:

kW (kilowatts)

Existing Power Factor ( % )

Desired Power Factor ( % )

From this information,now we can calculate the capacitor size for power factor correction.The formula to calculate the required kVAR is:

Factor from Table 1 below x kW = kVAR of capacitors required.

Calculation Example :

1 unit air-compressor ( 3 phase 415 VAC ) used an average of 90 kW with an existing power factor of 80%.The desired power factor is 95%. The factor value for this case is 0.421 to raise the power factor from 80% to 95% using table 1.

0.421 x 90 kW = 38 kVAR

So we need capacitor size 38 kVAR to get power factor 95% for 1 unit air-compressor 90 kW.

If working power (kW) or Present Power Factor are not known you can calculate from the following formulas to get the three basic pieces of information required to calculate kVAR.The best range for desired power factor is around 95% until 100%.

Are pf and efficiency of motors given nameplate of all motors?.
If no-load current is known(given in nameplate) can we estimate the size of capacitor required a) to start the motor (by reducing starting current)
b) to correct pf?.

hello, nice article!!! I am really impressed. Actually this is my first time reading your post. But I am very fascinated by the way you explained this simple method in sizing up a to improve power factor for induction motor and utility electricity. Thanks for sharing this information. Really good. I will be subscribing to your feed. Rest assured that I will read your future posts..

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